Printing head for thermal printer and method for manufacturing same

ABSTRACT

A plurality of heating resistors and their lead wires are formed upon a heat-resistive flexible film, and the flexible film is then curved and mounted upon a head structure in such a manner that the heating resistors are arrayed along a projecting edge of the head structure.

United States Patent Hiruma etal. 5] Feb. 6, 1973 [54] PRINTING HEAD FOR THERMAL 7 [56] ReferencesCited PRINTER AND METHOD FOR MANUFACTURING SAME UNITED STATES PATENTS ['75] Inventors: Kfnji Hiruma; Inawo Sugaya, both 3.161,457 12/1964 Schroeder et a] ..346/76R ofTokyo,Japan 3.327.314 6/l967 Zeuthcn ..-.346/76 R v 2.802.086, 8/l957 Fener ..l56/583 [73] Assignee: Ricoh Co. Ltd., Tokyo Japan, a Como/anon ofJapan Primary Examiner--- Henry T. Burke, et al.

122 Filed: Sept. 9,1911 [57] ABSTRACT [21] Appl. No.: 178,876 r A plurality of heating resistors and their lead Wires are formed upon a heat resistive flexible and the flexible film is then curved and mounted upon a Int. n "Bosh .head tructure in uch a manner the resistors are arrayed along a projecting edge of the Fleld 0f Search head structure 8 Claims, 2 Drawing Figures PATENTEBFEB' 61973 sum 2 UP 2 FIG, 4

FIG. 5

1 PRINTING HEAD FOR THERMAL PRINTER BACKGROUND OF THE INVENTION This invention relates to printing heads for so-called thermal printers, and to methods of manufacturing such heads.

A typical thermal printer includes a printing head which comprises a matrix of heating resistors. Printing is effected by exposing a heat-sensitive recording paper or the like to the head while passing electric current through selected ones of the aforementioned resistors so as to form on the paper a mosaic pattern or image of the heated resistors, e.g. a pattern constituting a letter, numeral or other symbol.

Thermal printing heads of the type described are commonly formed by various known micro-electronic techniques. Although thermal printers may advantageously be used (for example) as printers of electronic computers, they have the drawback that these known processes for manufacture of printing heads are undesirably complex and costly.

SUMMARY OF THE INVENTION of a method for manufacture of printing heads for thermal printers comprising the steps of forming upon a heat-resistive film a plurality of heating resistors and their lead wires as by vacuum evaporation or photoetching, curving or bowing the film, and mounting the heat-resistive film upon a head structure in such a manner that the heating resistors are disposed along a projecting portion of the head structure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a printing head embodying the present invention in a particular form;

FIG. 2 is a top view of the head of FIG. 1, illustrating the position of the printing head relative to a heatsensitive recording paper;

FIG. 3 is a view illustrating how a'numeral (three) is formed and recorded by the printing head of FIGS. 1 and 2;

FIG. 4 illustrates the pulse current wave forms to be applied to the printing head to form and record the numeral three as shown in FIG. 3; and

FIG. 5 is a view for explanation of the manufacture of printing head films used in the printing head shown in FIG. 1.

DETAILED DESCRIPTION In a printing head for a thermal printer in accordance with the present invention as illustrated in FIG. 1, a plurality of thin-film heating resistors 2 and thin-film conductors 3 (which serve as lead wires) are formed upon a surface of a heat-resistive and electrically nonconductive flexible film support 1 made from (for example) fluoroplastics, with the resistors disposed in a straight row (i.e. in spaced relation to each other along a straight line) on the film support surface. The support 1 is bowed or curved at an appropriate radius of curvature, with the row of resistors 2 disposed along the vertex of the bend or curve, and is securely fixed to a head structure 4 made from (for example) a heat-resistive plastic. The thin-film conductors 3 are individually coupled to separate flexible cables 6 at their connections 5. The head structure 4 is tapered at 7, defining a projecting rectilinear edge along which the outwardly facing resistors 2 are arrayed, in order to ensure satisfactory contact between the thin-film resistors 2 and a heatsensitive paper, and is carried by a shaft 8 which is coupled to a driving mechanism (not shown).

The relative position of the writing head with respect to the heat-sensitive recording paper is best shown in FIG. 2. That is, the heat-sensitive recording paper 9 is placed in close contact with the thin-film resistors 2.

As stated, and as best shown in FIG. 1, the seven thin-film resistors 2 are arrayed in a straight row for simultaneous engagement with the surface of the recording paper 9, and are displaced successively along the surface of 'the paper in five steps in the direction (perpendicular to the row) indicated by the arrow in FIG. 2. Therefore, a letter or numeral which is formed of a combination of (7 X 5) elementary mosaic areas may be printed upon the recording paper 9 as for example shown in FIG. 3. i

i In FIG. 3, a numeral three printed in the manner described above is illustrated. The letters L1L designate the seven thin-film heating resistors 2, and the letters T -T5 designate the number of steps. The pulse wave forms applied to the thin-film heating resistors 2 to print this numeral three (3) are shown in FIG. 4. That is, the pulse current is applied to the thin-film resistors 2,, 22, 2 and 2 at the time of step T1 so that these thin-film resistors dissipate heat to change the color of the elementary areas L L L and L7 in the column T At the time T the pulse currents are applied to the thin-film resistors 2 and 2-, so that the color of the elementary mosaic areas L, and L7 in the column T2 are changed by heat. In like manner. the pulse currents shown in FIG. 4 are applied to the indicated selected thin-film resistors 2 at T T4 and T so that the selected elementary mosaic areas change their colors. Thus the numeral three is printed as shown in FIG. 3. It is seen that any letter or numeral may be formed by applying the pulse currents to the selected thin-film resistors 2 as they are displaced.

Next referring to FIG. 5, the method for manufacture of the printinghead described hereinabove in column upon the heat-resistive flexible film support I by vacuum evaporation of a nickel-chromium alloy or photoetching. In the similar manner the thin-film conductors 3 are formed for example by vacuum evaporation of gold. In FIG. only a limited number of thin-film resistors and conductors 2 and 3 are shown for clarity, but his to be understood that any desired number of film resistors and conductors may be formed. Each printing head pattern (four patterns are shown in FIG. 5) is cut off, and bowed or curved with the thin-film resistors 2 disposed along the vertex .of the curve or bend, and securely fixed to the head structure as described in reference to FIGS. 1 and 2.

The printing head for a thermal printer in accordance with the present invention is simple in construction and light in weight and is adapted for mass production because the thin-film resistors and conductors may be formed upon the heat-resistive film by vacuum evaporation or photoetching. Thus the printing head may be manufactured at less cost than heads formed by processes heretofore conventionally used.

In the embodiment described above, the thin-film resistors have been described as being arrayed in one row or column, but it is to be understood that various variations and modifications can be effected within the scope of the present invention. For example,

a plurality of printing head structures may be stacked so as to form and record a letter or numeral without displacing in step the single printing head. In this case, the head structures 4 are not curved or tapered (as in the embodiment illustrated in FIG. 1), but are made thin with equal thickness and electrically insulated from each other. Furthermore, a plurality of printing heads capable of forming and recording a letter or numeral without shifting may be arrayed so that a plurality of letters or numerals may be formed and recorded simultaneously.

What is claimed is:

1. In a thermal printing device, in combination.

a flexible film member bearing a row of heating resistors and a plurality of leads respectively connected to said resistors;

a head structure for supporting said film member and having a projecting edge portion; and

means for making separate electrical connections to said leads for passing electric current through selected ones of said resistors;

said film member being bent around said edge portion with said row of resistors exposed and coincident with the vertex of the bend so as to be positionable in simultaneous contact with a surface of a recording medium.

2. A device as defined in claim I, wherein said heating resistors and said leads comprise thin metallic films adherent to a surface of said film member.

3. A printing head for a thermal printing comprising a heat-resistive flexible film support;

a plurality of heating resistors formed upon said flexible film support;

a plurality of lead wires formed upon said flexible film support and electrically connected to said plurality of heating resistors respectively;

a head structure to which said flexible film support is securely fixed; and

a lead wire plate having a plurality of lead wires respectively connected to said first-mentioned lead wires formed upon said flexible film support for connection with an external circuit, said flexible film support being curved or bowed at said heating resistors as the vertices and carried by said head structure. 

1. In a thermal printing device, in combination, a. a flexible film member bearing i. a row of heating resistors and ii. a plurality of leads respectively connected to said resistors; b. a head structure for supporting said film member and having a projecting edge portion; and c. means for making separate electrical connections to said leads for passing electric current through selected ones of said resistors; d. said film member being bent around said edge portion with said row of resistors exposed and coincident with the vertex of the bend so as to be positionable in simultaneous contact with a surface of a recording medium.
 1. In a thermal printing device, in combination, a. a flexible film member bearing i. a row of heating resistors and ii. a plurality of leads respectively connected to said resistors; b. a head structure for supporting said film member and having a projecting edge portion; and c. means for making separate electrical connections to said leads for passing electric current through selected ones of said resistors; d. said film member being bent around said edge portion with said row of resistors exposed and coincident with the vertex of the bend so as to be positionable in simultaneous contact with a surface of a recording medium.
 2. A device as defined in claim 1, wherein said heating resistors and said leads comprise thin metallic films adherent to a surface of said film member. 